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Monthly Archives: April 2012

I thought 3D scanning would be extremely painful to do without fancy equipment or complicated setups. However, Autodesk has a free (at least free for students) service called 123D Catch which allows you to upload pictures and have them processed as a 3D model on the cloud. Simply amazing. I just learned of this software today, and had a low quality test with my quadrotor on my desk:

Considering it was done with just 20 unfocused, low resolution photos that didn’t cover the entire span of the model, this 3D scan is amazing. I wish I had access to the source code.

Many applications for this. It’s a 3D printer’s dream to be able to record something on the field and have a replica of it printed in a few hours without ever having to touch or measure the reference object. That could be done by scouting with a quadrotor or drone, or just by hand or in a studio. The drone 3D model capture idea sounds great though. I’ll try to take some aerial photos and try to make a 3D model out of that later with the big quad. Another cool idea is taking underwater video and stitching that. More things to come.

Over Spring break I had some time, and I was missing my MiniQuad since I never had the chance to finish testing it. Though BigQuad was nice but heavy (a few pounds!), and MiniQuad was an attempt to reduce that (~60% reduction in weight), I wondered how much I could push the scale. Obviously, there are quadrotors that scale down extremely. My goal was to get under 400 grams, and still hold a reasonable payload. And at that scale, with 10-15g motors, things get cheap. Everything is at least a third to a quarter of its large scale counterpart in pricing, which further encouraged me.

I was able to laser cut a small piece in the scraps bin that fit the dimensions for my frame. With a 200mm square profile, the frame contributes to nearly half of the weight. After my Hobbyking order arrived a few days ago, I was able to fit everything to this:

It was a modification to my original design. Though I originally planned to weigh around 400 grams, I could not find suitable propellers for the motors. These 5×3’s I believe are smaller than the recommended size, but they were the only size left that were not on back order. Nevertheless, the further reduction brings this little machine to 250 grams final weight. Probably, with some carbon fiber, I could reduce the weight to 180g or so, but the 250 grams is good for now.

Modifications from previous designs include an XBee radio over the Spectrum radio system I was using before, a digital IMU with 3-axis magnetometer, and an Arduino Nano over Uno. The switch to XBee will hopefully allow me to guide by computer, with a little FPV GUI showing important flight data stuff, and allow me to gather data remotely. The last part is crucial, as the most compelling reason I wanted to make this scaled down quadrotor was to function as a mapping drone. With (potentially) stereo cameras, its magnetometer, and a potential GPS system, this little quad will be able to determine heading and location. Some contact sensors will be placed around the quadrotor to allow the robot to bump into things and detect obstacles, and its small size will ultimately allow it to fly indoors relatively safely and navigate through halls, doorways, and windows.

I know I’ve been branching out to too many projects at this point. I have Spirit’s armor left to upgrade, MiniQuad to fly, and my robot arm left to automate. I’ve been meaning to go into more depth with bioprinting the plant cells, getting around to that drop on demand inkjet toolhead expansion, and finish upgrading the build surface. I need time to focus on a single thing. But school, and school takes priority. It’s the mindset that this coming summer will provide that extra gap of time I’ll need to get these things rolling again. The Shadow Fox project too, has been put on hold until next semester. At least temporarily, as the funds are lacking. I need to refine my design heavily before investing any time into actuator tuning and research (currently between PAMS, HAMS, and serial elastic connected motors). To aide that, I have a dozen or so sub-2$ turnigy servos to make a miniFox to experiment with serial elasticity as well as dynamic walking gaits over the summer. As for school, I’ll be busy for the next few weeks. I’m making a RoboChoir.